Additives that claim to break down polyethylene and polyethylene terephthalate don’t work in common disposal situations, such as landfills or composting, a new study from Michigan State University (MSU) has claimed.

The results are a culmination of a three-year study that focused on five additives and three categories of biodegradation, which cover the majority of methods available on the market today.

The team studied biodegradation with oxygen, such as in composting; biodegradation without oxygen, such as in an anaerobic digester or a landfill; and simply burying plastics.

“There was no difference between the plastics mixed with the additives we tested and the ones without,” said Rafael Auras, co-author and MSU packaging professor.

“The claim is that, with the additives, the plastics will break down to a level in which microorganisms can use the decomposed material as food. That simply did not happen.”

The study was funded by packaging companies because they “wanted scientific proof to evaluate the products and disposal approaches that are available to them to break down plastic”, said Susan Selke, co-author of the study and also MSU packaging professor.